ABSTRACT
This chapter covers delay between buying and consuming, demand for a varying product, changes in demand and demand for durable goods. It is convenient for analysis to assume that a product is consumed immediately it is bought, but of course it is far more common for there to be some delay and perhaps a storage period. Much of the economic theory on the quality of durables has been carried out in abstract models of consumer choice, which defined the quality of a product as the life of the product. Purchases may change while demand remains constant, even though quality and price are also unchanged. This has long been recognized by marketing, and the implications on product launching, brand loyalty, and market share have been explored fully in the literature. In economics it has normally been ignored, with the result that many of the models built up cannot cope with this touch of realism.
